This invention relates to medical instrumentation, and more particularly, to a method and system for the noninvasive detection of zinc protoporphyrin in erythrocytes.
It has long been recognized that the ingestion of lead bearing compounds by humans may lead to lead poisoning. If such poisoning is not detected and treated, irreversible neurological damage may result. In the prior art, the measurement of lead in the blood has been the primary approach for detecting lead poisoning. However, this approach is difficult and relatively expensive to implement for large scale population screening. Recently, it has been recognized that the compound zinc protoporphyrin (ZPP) accumulates in erythrocytes (red blood cells) in humans exposed to low toxic levels of lead. It has further been observed that ZPP is characterized by a red fluorescence emission spectrum (having a strong peak at 590 nm and a weak peak at 640 nm) in response to excitation with blue light (at about 420 nm). In view of these observations, protoporphyrin fluorescence detection procedures have become accepted methods of screening for lead exposure. Furthermore, such procedures have also been determined to be effective in screening for iron deficiency anemia (such as may be due to bleeding, inadequate diet, heredity diseases) and for the detection of exposure to certain drugs, for example, the experimental anti-cancer agent cis-diamminedichloroplatinum.
In the prior art, ZPP fluorescence detection has been accomplished only using invasive techniques, that is, where a sample of blood is first obtained, and then analyzed using the ZPP fluorescence detection technique. This type of invasive procedure requires considerable effort in terms of obtaining samples, maintaining these samples, and performing and recording the test results. Accordingly, screening of medium to large size populations is quite difficult using the prior art approaches.
Accordingly, it is an object of the present invention to provide a method and system for performing the non-invasive detection of ZPP concentration in erythrocytes.